Snip off the connector of the original fan, and strip the wires. We’re going to re-use this connector with our new fan.
You’ll also have to cut off the connector of the Noctua fan, and strip those wires back. At this point it would be best to put a small piece of heat shrink over each of the three wires, and if you want to make it tidy afterwards, a larger piece of heat shrink over the entire thing. That way you can insulate each wire, and also get that completed “stock” look when you’re done.
IMPORTANT: Install a 10k ohm resistor that bridges the 5V line with the Signal line, to increase the power draw of the fan. If you don’t do this step, your Dreamcast will either boot for a few seconds, then shut itself off, or fail to turn on at all.
Wire it up correctly using the pinouts below, making sure that you connect 5V to 5V, Ground to Ground, and Signal to Signal. Don’t worry about the mismatched colours. If you want to lower the speed of your fan below the rated 4500 RPM, see below.
Thanks for the detailed instructions. Actually, I found an affordable 3D printout already including the cable with the resistor put into place and a plug adapter. All tools needed was a little screw driver. So 20 years after production, the Dreamcast is finally as silent as it should have been. Absolutely worth the money and it’s completely reversible.